Time-to-go mechanism



Sept. 19, 1961 E. E. MITCHELL TIME-TO-GO MECHANISM Filed DeO. 1'?, 1957 INVENTOR.

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United States Patent 3,000,568 TINE-TO-GO MECHANISM Edward E. Mitchell, New Hartford, N.Y., assignor to the United States of America as represented by the Secretary of the Air Force Filed Dec. 17, 1957, Ser. No. 703,464 6 Claims. (Cl. 23S-193)' This invention relates to a mechanism for providing a continuous indication of time-to-go to an event such as an attack on an enemy bomber.

One object of the invention is to provide a device which will give a continuous indication of the time-to-go to an event during the interval between the times that data is Ireceived from the data link or in the absence of such data.

This and other objects will be more fully understood with reference to the following detailed description when taken in connection with the drawing wherein the single figure is a circuit diagram partially in block form showing one embodiment of the invention.

Prior art time-to-go devices produce a new output voltage representing the time-to-go to an event, suchas to the time of an attack on an enemy bomber, each time new information is received. The output of such a device, however, will remain substantially constant between the times that new information is received. The device of this invention is for the purpose of giving approximate and continuous indications of time-to-go during this interval of time. Since the usual time interval is known, an escapement motor can be set to operate at a particular speed so as to continually supply a voltage whichvcan be subtracted from the output of the time-to-go device to thereby give a voltage more nearly proportional to Ithe exact time-to-go.

Referring to the drawing, reference numeral 10 refers to an accurate escapement type timing motor which operates a linear potentiometer 11 through an electromagnetic clutch 12. The escapement motor 10 operating at ya precise speed moves the control contact 13 of the potentiometer 1&1 at a constant rate thereby causing a gradually increasing portion of the 20-volt, 40G-cycle reference voltage to be applied to the secondary of the transformer of T1. The polarity of the primary and secondary windings of transformer T1 are chosen such that the voltage applied to the secondary is subtracted from the analog voltage applied to the primary from the data link long time storage unit 14. The motor may be a variable speed motor to make the apparatus adaptable for various uses; however, for any one application, the motor is operated at constant speed. If the speed of the escapement motor is properly chosen the voltage appearing at the output 25 is proportional to the time-to-go extrapolated exactly from the previously received data. When new time-to-go data is received in the storage unit 14, relay 15 closes its contacts momentarily. The circuit through relay 16 is then completed and it also closes its contacts. =The current through the relay contacts 18 and lock-down resistor R1 causes relay 16 to remain locked down until switch contacts 17 are closed. Relay contacts 19 close the circuit from the 28-volt supply to the electromagnetic clutch 12 causing this clutch to release. A reset spring 20 then returns the potentiometer 1'1 to its zero position where arm 21 closes switch contacts 17. When contacts 17 are closed both sides of the winding of relay 16 are connected to ground so that no current can ow therethrough. Relay 16 is therefore deenergized and relay contacts 18 and 19 are opened. When contacts 19 are opened clutch 12 is allowed to reengage for the next timing cycle. When the time-to-go reaches zero voltage amplitude discriminator 22 actuates a relay 23 to stop the operation of the escapement motor 10. A voltage amplitude discriminator 24 may sired value of time-to-go voltage. There are many suitable voltage amplitude discriminators which may be used, one of which is shown in FIGS. 9-41 on page 359, vol. 19 of M.I.T. Radiation Laboratory Series. In one possible mode of operation with this voltage discriminator, the time-to-go voltage can be applied at el and the discriminator internal reference voltage can be applied at e2 with relay 23 connected at ep so that the tube is cut ol when the time-to-go voltage reaches a certain predetermined value corresponding to time-to-go equal to zero which may be set by the choice of the reference voltage. The circuit constants can be selected so that relay 23 will operate when the tube is cutoff. Other modes of operation for the discriminators to produce the same result will also be obvious to those skilled in the art and the particular mode chosen forms no part of this invention. The output at 25 may be applied to 'a meter to indicate the time-to-go. There is thus provided a device which will give a continuous indication of the time-to-go to an event during the interval between the times that data is received from the data link.

Although one embodiment has been described in some detail it will be understood that numerous changes may be made without departing from the principle and scope of the invention.

I claim:

1. A device for providing a continuous indication of time-to-go to an event from intermittent -data comprising; means for producing a rst voltage proportional to said data, means for producing a gradually increasing second voltage, means for subtracting said second voltage from said first voltage to produce lan output voltage proportional to time-to-go and means responsive to an output signal from said lirst volt-age producing means for resetting said gradually increased voltage to zero whenever any new data signal is received.

2. A device for providing continuous indication of time-to-go to an event from intermittent data comprising; means for producing a step voltage proportional to said data, a second voltage source, means for subtracting a portion of the voltage from said second source from said step voltage to thereby produce an output voltage proportional to time-to-go, means for gradually increasing the portion of said second voltage which is subtracted from said step voltage, and means responsive to an output signal from said step voltage producing means for resetting said last named means to zero voltage in response to a new data signal received.

3. A device for providing a continuous indication of time-to-go to an event from intermittent data comprising; means for producing a step voltage proportional to said data, a Ksecond voltage source, means for subtracting a portion of said second voltage from said step voltage to produce a voltage proportional to time-to-go, a potentiometer for gradually increasing the portion of said second voltage which is subtracted from said step voltage, a constant speed motor for controlling the movement of the potentiometer slider and means responsive to an output signal from Asaid step voltage producing means for returning said potentiometer to its zero position whenever Ia new data signal is received.

4. A device for providing a continuous indication of time-to-go to an event from intermittent data comprising; means for producing a step voltage proportional to said data, a second voltage source, means for subtracting a portion of said second voltage from said step voltage to thereby produce van output voltage proportional to time-to-go, a potentiometer for gradually increasing the portion of said second voltage which is subtracted from said step voltage, a shaft connected to the slider Patented Sept. 19, 1961 4 said clutch to reengage when the potentiometer reaches its zero position.

6. A device as claimed in claim 4 wherein there is a means controlled by said output voltage for stopping said 5 constant speed motor when the time-to-go is equal to zero.

References Cited in the le of this patent UNITED STATES PATENTS Herbst Mar. 14, 1950 

